We demonstrate a reconfigurable filter based on the stimulated Brillouin scattering (SBS) effect in fiber with 3 dB bandwidth from 20 to 500 MHz. We analyze the influence of pump lines and pump spacing on the filter and propose an SBS‐based filter with low passband fluctuation by vectorial modulating multi‐lines pumps. The filter passband fluctuation is decrease to 0.49 dB by precise controlling the pumps' lines, pumps' spacing, and vector signal modulated rate. The proposed single bandpass microwave photonic filter also successfully demonstrates a wide‐band tuning range from 1 to 20 GHz and high out‐of‐band rejection ratio of over 40 dB. The SNR performance of the proposed SBS filter is analyzed and shown the potential capability in the fields of microwave signal processing in satellite communications, electronic warfare, and radar systems.